The aim of this proposal is the examination of the mechanism for phosphoryl transfer in enzyme catalyzed reactions. The experimental approach features an interplay between complimentary nonenzymatic and enzymatic investigations in order to establish kinetic and sterochemical criteria for distinguishing between the two limiting mechanisms for phosphoryl transfer -namely the dissociative (metaphosphate) and associative (pentacovalent phosphorus) pathways and to define the nature of the catalytic process, i.e. the identity of the rate-limiting step(s) and the life times of the associated species. Enzyme reactions to be investigated include fructose-1, 6-bisphosphatase (liver), selected owing to its importance in gluconeogenesis as well as the opportunity afford for investigating the influence of allosteric modifiers on the catalytic mechanism and acid phosphatases (wheat germ, prostate), the latter being amenable to stereochemical investigations employing a chiral phosphorus center. The mechanism of action of fructose-6-phosphate 1-phosphotransferase, probed with substrate analogs, will be contrasted to that of the bisphosphatase. The ubiquitous occurrence of phosphatase enzymes and their elevation in certain disease states, specifically diabetes and prostate carcinoma for the aforementioned enzymes, suggest that specific inhibitors or assay reagents designed on the basis of their mechanism of action would be of diagnostic or therapeutic value.